I know there are names for the parts but I don't know them so bear with me. Make sure the jets are clear, not all banged up and aimed at the flats. Make sure the flats are just that, flat with a clean edge on them. A lot of the output depends on engine speed and location of whistle also size of whistle. I have tried the "T" size and was unimpressed with it's sound. The one I have on the car now is about 1 foot on the longest tube and it does ok. At some speeds it sorta sounds like an asthmatic tea kettle and can hear each firing of the cylinders.

i posted on the other thread, mine works best at hyway speed, and down hill. why? maybe engine is breathing better when not under load? dunno, one thing for certain, its makes a sweet tone when by yourself, and when some folks are nearby and you blow the whistle for them it will sound sick